Flip Side
by The Heart's Notebook
Summary: The time has come for another spirit to join the Guardians, however not one but two have been chosen. One of light and one of dark, but the others do not know who is who. Can the Guardians figure out which is the real candidate before the world is thrown into darkness once more? JackXOC pairing.
1. Prologue: Chills

_**Co-writer: Celsius Fate!**_

 _ **Flip Side**_  
Prologue: Chills

They did it.

It was the day after Christmas.

The Guardians were able to deliver all the presents to every child in the world just in time for Christmas morning. So, they decided to celebrate with a little race. It was Jack, Bunny, North, and Sandy against one another with Tooth being the referee. Tooth giggled gleefully as the boys passed by her and some of her fairies.

"C'mon cottontail," Jack smirked as he led the way around North's place at the Pole, "Can't you do any better than that?" He slid bare-foot down the track of solid ice, twisting and turning throughout the place while laughing merrily.

"Ah, shut it, show pony," Bunny stepped on the gas on the huge red toy airplane the Yetis built. "You haven't won yet, mate!" the Guardian of Hope added as he turned right.

Sandy smiled as he closed in on Bunny on a cloud of dream-sand. He frowned when North passed him on a smaller sleigh that was being pulled by two reindeer. Not wanting to lose to the others, Sandy sped up in order to catch onto North's trail.

"Here I come!" North chortled with a Russian accent.

Jack laughed joyfully as he approached the finish line. He skid to an abrupt stop when he heard a female voice talking indistinctly. Slowly a vision took over his sight, one that completely entranced the Guardian of Joy as his legs stopped in the middle of crossing the finish line.

* * *

 _"Belle!" A twelve year old girl with long brown hair, brown eyes, and pale skin was up on a roof of a high-rise in the city._

 _She was shaking like a leaf, teetering near the edge of the roof, with the old bricks slowly giving way under her feet. One wrong move and she will plummet downward onto the pavement below, effectively ending her life._

 _"It's alright, Rachael," the older girl, Belle, smiled softly. Her long bleach blonde hair flew into her wavering honey-brown eyes._

 _"You're going to be all right," Belle got closer._

 _"I don't want to die, Belle," Rachael sobbed._

 _A single brick began to crumble quickly._

 _"Shhh," Belle soothed, "I'm not going to let that happen, sweetheart." Belle began to run forward just as the younger girl started to fall, "RACHAEL!" Belle grabbed her little sister's arm, pulled her up, and tossed her onto the cement roof._

 _"BELLE!" Rachael screamed._

 _A blood-curdling scream ripped from Belle's throat as the brick gave way completely under her feet._

 _Belle crashed onto the sidewalk below._

 _"NO!" Rachael screamed._

* * *

Bunny raced past Jack to the finish line and began boasting and laughing as the others crossed right behind him. When the Guardian of Joy didn't react to this, the others focused their attention onto the winter spirit, noticing how he was standing still and completely unresponsive. Tooth hesitantly flew forward and waved a hand in front of her friend's face, but there was no reaction from Jack.

They froze when Jack suddenly screamed out loud, and that's when they saw two tears run down his face.

"Jack? What's wrong?" Tooth rested a hand on the younger Guardian's shoulder.

Jack looked at her as the vague vision left him.

"What is it, mate?" Bunny wondered.

"I just...I just saw a girl die," Jack swallowed thickly, feeling two wet trails down his face.

"What? What are you talking about, mate? No one died," Bunny said in a perplexed voice.

"I know. I mean I had a vision of a girl dying while saving her sister's life...like I did," Jack explained softly.

"What were their names?" North inquired curiously.

"The younger sister was named Rachael and the one who died was Belle, her older sister," Jack answered.

No one responded for several moments.

"Are you sure those were their names?" Bunny arched a furry brow at the winter spirit.

Jack nodded.

The older Guardians all looked at each other.

They all proceeded to glance up at the sky that was visible through the opening, thanks to the giant telescope that stretched through the ceiling. The moon slowly came into view as clouds dispersed.

It was shining brightly, casting its gentle rays onto the Guardians, basking them in a warm light.

"Man in the Moon, did you show me that vision?" Jack asked.

The Moon cast its glow over Jack like a spotlight in response.

"What are you trying to tell me?" he continued, hoping the moon would give him some answers.

The Man in the Moon panned the beam to the center of the group where the crystal was hidden. The symbol on the floor slid open and the crystal rose up to the surface, glowing increasingly brighter until it stopped in front of the Guardians. This was exactly what happened several years ago when Jack was chosen to become the newest Guardian. Could the same thing be happening again?

A question mark made of sand appeared over Sandy's head.

"He's choosing a new Guardian!" Tooth exclaimed excitedly.

"But why? What does this have do with the vision?" Jack drew closer to the glowing crystal.

"Have no idea," North replied with a shrug.

Slowly the crystal projected Manny's choice.

There were not one, but two Guardians depicted. Both wore what appeared to be dresses with boots, and masks that covered their faces from view, with hair that went down towards their waist.

Two female spirits.

The older Guardians gasped in surprise.

"What is it? What's wrong?" Jack asked them.

"It can't be," Tooth's wings stopped beating as she landed on her feet next to Bunny.

"He picked the Twins? Of all the Guardians to choose from, he _had_ to select the Twins" Bunny groaned.

"The Twins?" Jack arched a snow-white brow.

"You see...Jack, the Twins are like us; humans who became spirits after their death," Tooth began explain.

"I'm with you so far," Jack said. "But I don't understand. Why is that a problem?"

"The Twins are sisters, obviously," Bunny added, "But the thing is, they've been giving us problems for years. One more than the other, but we can't tell which one is which."

"Why?"

"They're _identical_ twins," Tooth replied.

"That makes a lot more sense," Jack rested his staff against his shoulder. "Right, here's another question. Why would Manny pick them if they're a lost cause?"

"We don't know," North shrugged.

"I asked the same question when he chose you to become a Guardian several years ago," the Guardian of Hope muttered quietly.

The Guardian of Memories elbowed her friend sharply and gave him a look.

Bunny sighed heavily and focused his attention onto one of the Elves waddling around with a tray of cookies.

Sandy thought for a minute then looked up at Jack and tugged on his sleeve.

"What is it, Sandy?" Jack looked at the silent Guardian.

Sandy pointed at Jack then at his own eyes.

"You got a point, Sandy," Jack stated.

"What point would that be, mate?" Bunny asked.

"Well, what if the older girl in my vision is the one that the Man in the Moon deems to be the good one?"

"Okay?"

"However if they're identical, how are we going to be able to tell which one is Belle?" Jack mused.

"What if...? Oh, never mind," Tooth said exasperatedly.

"What is it, Tooth?" North looked at her with the others.

"I was just thinking; what if Manny only showed the vision to Jack because he believes that Jack has a connection to Belle? That Jack is the one who can tell one apart from the other?" the Guardian of Memories explained carefully.

"That's an interesting theory, Tooth, only I've never seen the twins before," Jack stated.

He began to walk away from the others after he spoke.

"Wait, Jack, where are you going?" Bunny asked.

"I promised Jamie that I would go and see him," Jack looked at Bunny with a grin. "You wanna come too, Bunny? You can see Sophie."

"The lil' ankle-biter?" Bunny smirked.

Jack nodded.

"I'm in," he went up to Jack.

"But Bunny, what about the twins?" Tooth flew over to them.

"Relax, Tooth, it'll take us a while to find them. Looking for them aimlessly right now isn't that important," Bunny stated.

He and Jack left through one of his many tunnels and appeared outside of Jamie Bennett's house.

* * *

The duo sneaked in through Jamie's bedroom window to see the boy fast asleep. Bunny quietly went into Sophie's room to find her wide awake, sitting in the middle of the floor and playing with a bunch of stuffed animals. She looked up from her stuffed bunny and a huge grin broke across her face.

"BUNNY!" she squealed and ran towards him.

Bunny crouched down and held out his arms to the three-year-old, "There's my lil' ankle-biter," he smirked as he hugged her tightly, while Sophie cuddled up against his chest.

The Guardian of Hope stroked Sophie's hair softly as he sat down on the bed with her clinging to his fur.

He cuddled up with her and waited for her to fall asleep.

* * *

Jack sat at the foot of Jamie's bed, conjured up a small snowflake, and blew it over to Jamie. The snowflake landed on Jamie's cheek rousing the boy awake, prompting him to look up to find the winter spirit at the foot of his bed.

"Jack!" Jamie smiled and hugged the Guardian of Joy.

"Hey kiddo," Jack chuckled and returned the embrace.

"Jack, can I ask you a question?" Jamie looked up at Jack as he pulled away to sit in front of the Guardian.

"Sure, what's up?" Jack asked.

"Is there a new Guardian?" Jamie inquired quizzically.

"No, not yet, why?" Jack arched a brow.

"For the past few days I keep seeing this teenage girl sitting outside my window. She sings to me in my sleep," Jamie explained.

"Sings to you?" Jack repeated.

Jamie nodded.

"What did she look like, Jamie?"

Jamie looked at the window and started shaking. "She's right there," Jamie pointed at the silhouette of a girl hovering outside his bedroom.

Jack was on his feet in a instant, his staff poised for an attack. He looked at the window and saw a pair of glowing blue eyes staring back at him through a mask. The girl's eyes gave an eerie glow upon her face.

She flew away from view when she caught sight of Jack.

"Jamie, stay here. I'll be right back," Jack told the boy.

Jamie inclined his head and Jack went after the spirit.

* * *

The Guardian of Joy went up to the roof to discover a teenage girl staring up at the moon. She was wearing a purple dress that went down towards her knees, with black lace-up boots that wrapped halfway up her legs. Her waist-length black hair billowed in the chilly breeze that radiated off of Jack. However the part that caught his attention was the mask on her face. One side covered her left and was tinted gold, while the other covered her right and was colored silver.

Jack shook his head several times and reorganized his thoughts.

 _'How dare she frighten Jamie like that!'_ he thought.

"Hey! What do you want?" Jack growled angrily.

"I'm not here to hurt Jamie. If that's what you're asking," she said, turning to Jack. Her eyes were still glowing, enough to give Jack the chills the more he stared.

"Then what do you want? Who are you?" Jack demanded.

"You ask a lot of questions," she turned away.

Jack blocked her path, "I have the right to. Now answer me!"

She merely rolled her eyes at him.

"Answer me!" Jack snarled.

"I know what you said Jack, I'm not deaf."

They glared at each other for a minute until she answered, "My name is Luna and I was merely going to sing Jamie to sleep. He's been having trouble sleeping as of late."

"Right, let's say I buy that. What does Jamie mean to you?" Jack crossed his arms over his chest.

"Are you jealous, Jack? Jealous that he might be friends with other spirits besides yourself?" Luna teased.

When Jack didn't answer, Luna disappeared into the night after giving him a mock salute.

"A spunky sheila, ain't she?" Bunny stepped out from behind the chimney top.

"Who was that?" Jack asked his fellow Guardian.

"That would be one of the twins, mate."

Jack's eyes widened in shock at Bunny's answer.

 _She_ was one of the twins?

* * *

 _ **To Be Continued...**_


	2. Crossing a Line

_**Flip Side**_  
Ch1: Crossing a Line

Jack went back into Jamie's room after Bunny left for the Pole to inform the others of what had happened. He saw Jamie on the bed waiting patiently for him, the latter scared based on the way he trembled. The winter spirit couldn't blame him for it, since the poor kid was being spied on while he slept. If anything, it was more of an invasion of privacy even if the intentions were noble.

"It's alright Jamie," Jack assured, pulling the child closer to him.

"She'll come back," Jamie sniffled a little.

The Guardian of Joy sat down on the bed next to the boy, "It'll be alright Jamie. You have me and the others to protect you," he repeated firmly.

Jamie climbed into the Guardian's lap as tears trickled down his face.

He hugged Jack tightly, "I'm scared, Jack. I really am."

Jack embraced Jamie, "Shhh. Everything's going be all right, Jamie. I won't let her or anybody else hurt you or Sophie, I promise."

It took a while but Jamie finally fell asleep in his lap after much reassurance from the former that nothing will happen to him. Jack kept his eyes trained on the window the entire evening, watching for signs of one of the twin's return. No one appeared for the night, almost as if the twin from earlier sensed that he was in the house and was currently avoiding it like the plague.

"Jack?" a small voice whispered.

Said Guardian turned his head to the right upon recognizing Tooth's voice, the Guardian of Memories appearing from a portal from one of North's snow globes. Jack made a sign with his finger, then pointed at the slumbering Jamie on his lap.

"What's the matter?" he inquired, carefully shifting his body so as not to jostle Jamie awake.

"Bunny informed us that you ran into one of the twins earlier?" Tooth sat down beside her friend.

Aquamarine orbs darkened at the mention of the twin from before.

"Did something happen between you and her?" the Guardian of Memories went on.

"She said something about Jamie being unable to sleep, so she sings to him at night."

"She sings to Jamie?" Tooth echoed.

A nod.

"I don't know what she wants but if Jamie is scared of her, I'm going to protect him until he feels safe again."

Tooth reached a hand out to gently stroke the child's soft locks, smiling fondly at how close he had grown with all the Guardians in general. Her mind went back to the day they fought Pitch, and how every child in the world stopped believing in them, except for Jamie. If it weren't for him and his friends, they never would have defeated the essence of Nightmare and sent him back to the pits where he belonged.

They owed Jamie more than their lives.

"Here," Tooth handed Jack a small snow globe.

"What's this for?" Jack wondered.

"Give it to Jamie," Tooth whispered.

That was all she had to say.

Jack nodded, then Tooth went back to the Pole.

* * *

The next morning Jack waited for the boy to wake up. As he suspected the twin didn't return the entire evening, though the Guardian of Joy was on alert nonetheless. He couldn't risk having her somehow interfering in Jamie's personal life.

"I have to go now, Jamie," He told the boy after a while.

Jack handed the globe to Jamie.

"What is it?" Jamie looked at the transparent orb.

"It's a snow globe. If you and Sophie are ever in any danger don't hesitate to use it. All you gotta do is tell i where you want to go and break it."

"Yeah," Jamie nodded.

Jack knew that Jamie didn't want him to leave, but he had to help look for the twins. The sooner they were found the better and the safer Jamie and Sophie would be.

The Guardian of Joy slipped a balled fist under the boy's chin and made him look at him.

"Do you trust me, Jamie?" Jack asked him.

Jamie didn't answer.

"Do you?" he repeated.

"Yes," Jamie nodded.

A smile broke out on the winter spirit's face and he brushed the child's tears away,

"Then you should know that I won't let her hurt you or Sophie. Everything's going to be alright."

Jamie sniffled and smiled as best he could at the Guardian of Joy.

It pained the former to see such an expression upon his friend's face, and Jack silently vowed to take care of the twin business once and for all. Though it felt uneasy to him to leave Jamie alone, the winter spirit felt slightly better knowing the child had a snow-globe to use in case of emergencies. If the twins did return to bother him, then he can just teleport himself and his sister to the north pole.

"I'll be back soon, and remember to say where you want to go if you need to use the globe."

Giving the child one last look as he lingered near the window, Jack called the wind to carry him to where the others were.

* * *

"How can it be this hard to find them?" Jack sighed in frustration as he and fellow Guardians gathered around the globe at the Pole.

They had been searching and searching for hours and days on end with no results.

Luna never came back around Jamie or Sophie.

Jack checked in on them every chance he got. Last time he saw them, Jamie was so exhausted he couldn't keep his eyes open. The winter spirit had stayed with the boy that night, and the latter fell asleep despite the lack of warmth radiating from the Guardian.

"There's got to be something we're missing," Bunny stood beside Jack.

The two had set aside their differences and disagreements after the battle with Pitch. After finding out that Guardian of Joy made Jamie believe in him again, he and Bunny had become best friends.

"But what could it be," North wondered.

He had just returned from searching with Sandy, and was in the middle of removing his shapka when a portal suddenly appeared behind the Guardians.

"Jamie!" Jack rushed towards the boy as he and Sophie stumbled onto the floor.

He noticed that the boy had a broken arm, along with sporting several bruises and cuts. Sophie too was unconscious with several bruises, and a cut along the bottom half of her lip, with her shirt ripped in several places. The mere sight of the two children was enough to send Jack into a mindless rage, though the Guardian fought to keep it under control, not wanting to unleash his rage inside North's home.

Bunny nearly slipped as he hurried to kneel beside Jack.

"What happened?" the Guardian of Hope hissed angrily.

"Luna came back and tried to kill us!" Jamie sobbed, clinging onto the winter spirit in despair.

Jack's eyes widened with shock, then darkened dangerously with rage. The boy shuddered at the deadly glare on his friend's face, this being the first time witnessing such a dark look from the normally joyful Guardian. Jamie suppressed the urge to shudder, instead focusing his attention onto his little sister, the latter being tended to by a distraught Bunny.

Jack stood up.

All eyes in the room focused upon the raging Guardian of Joy.

An angry snarl erupted from deep within Jack's throat as his grip on his staff tightened significantly.

Jamie backed away slowly when he saw that the Guardian's eyes were beginning to glow with anger.

"That does it! She crossed a line," Jack growled darkly.

He opened a portal with a snow globe.

"Wait, Jack, where are you going? You can't hurt her, she's been chosen by the Man in the Moon to become one of us." Tooth inquired nervously.

"You don't seriously expect me to let her get away with all of this, do you? Chosen or not, no one hurts my friends!" Jack hissed at her, eyes narrowing in anger.

Tooth backed away from the Guardian, frightened by what she was witnessing. The normally calm and joyful Jack was now radiating with anger and rage, which was something the others were not accustomed to seeing.

"Jack..."

"NO!" Jack roared, slamming his staff against the floor.

A sudden blast of freezing cold wind knocked his friends off of their feet, while ice formed all around the walls, ceiling, and even frosted over North's giant globe. Jamie and Sophie were shielded by Bunny, the human boy trembling in fear as he peered over the Guardian of Hope's arm to find the entire area encased in ice. His sister was currently crying loudly in Bunny's chest, frightened by what just happened. North, Tooth, and Sandy managed to duck behind a table just in time as the trio cautiously stuck their heads out.

"Look at what he did to my home," North lamented.

"Where's Jack?" the Guardian of Memories asked, slowly hovering in the air.

The Guardian of Joy was nowhere to be found.

* * *

 _ **To Be continued...**_


End file.
